WASHINGTON  Defense Secretary Robert Gates has submitted a defense budget that scraps Army plans for new combat vehicles — after spending almost $14 billion in research and development costs — because they won't adequately protect troops from roadside bombs.

Gates also raised questions about the Marines' new amphibious landing craft because, saying it's unclear how often U.S. forces will need to storm beaches. The Expeditionary Fighting Vehicle (EFV) already has cost at least $1.2 billion in research and development.

Gates' action follows his push to accelerate delivery of Mine Resistant Ambush Protected vehicles (MRAPs) to Iraq to replace Humvees after generals and members of Congress complained the Humvees provided inadequate protection from bombs planted by insurgents.

Failure to learn lessons about improvised explosive devices — which have accounted for at least half of troop deaths in Iraq and are a growing menace in Afghanistan — doomed the eight types of vehicles included in the Army's Future Combat Systems.

Gates says the vehicles' flat bottoms that sit 18 inches off the ground in the original design reflected "no lessons learned" from combat in Iraq and Afghanistan. The MRAP, by contrast, has a V-shaped hull that deflects roadside blasts and makes survivability far more likely.

The Marines new amphibious landing craft, is also in danger because it lacks the MRAPs V-shaped hull, said Dakota Wood, a military analyst at the Center for Strategic and Budgetary Assessments.

Insurgents using roadside bombs in Iraq and Afghanistan exploited the same weakness in Humvees, the military's longtime workhorse vehicle. Flat-bottom vehicles built close to the ground absorb explosions and transmit the impact to the troops inside.

That was a key reason, Gates said, in his decision to recommend canceling the Army's new vehicle program.

The Army's premise that less weight, greater fuel efficiency and more technology to detect threats would compensate for less armor was seriously flawed, Gates said recently during a speech at the Army War College.

It wasn't mid-2007 — when roadside bombs attacks had reached their peak of more than 2,500 per month in Iraq — that vehicle designers began to study ways to put a V-shaped hull on the infantry carrier, Gates said. That vehicle was built to carry 11 troops into battle.

The almost $14 billion in development costs for the Future Combat Systems also includes money spent on unmanned aerial vehicles, electronic sensors and other parts of the system. Total estimated costs for the system were about $160 billion; about $90 billion would have been spent on the vehicles.

The late realization of the need for a V-shaped hull resulted in "ad hoc" armoring that added too much weight to the vehicle, Gates said. He now proposes to spend the money saved on scrapping the vehicles for a new fleet that acknowledges the threat from improvised explosive devices (IEDs).

Gates told the Senate on Thursday that IEDs are "a threat that, considering their effectiveness, we should expect to see in any future conflict."

The Army's failure to modify its plans faster reflected a Cold War mentality to developing weapons, Wood said.

"They were not doing threat-based planning," Wood said. "When it was designed, they had not physically experienced roadside bombs."

The Marines have been developing their vehicle since the mid-1990s. It has a crew of three and is built to quickly carry 17 combat-equipped Marines from ships to shore. Estimated research and development costs have increased from $1.5 billion in 2000 to $3.6 billion last year, according to the Government Accountability Office. The cost per vehicle increased from $8 million to $23 million.

The amphibious vehicle's flat bottom is fine for skimming the sea at high speed, Wood said, but it lacks the characteristics necessary for survival on the ground.

Marine Corps Commandant Gen. James Conway said Wednesday the EFV wouldn't be used "in an IED environment." Armor can be added to it once it reached shore, he said.

Gates, in remarks made at the Naval War College, said military planners need to determine how often Marines will be called on to storm ashore. Currently, the Marines' two top missions are in the western desert of Iraq and in land-locked Afghanistan.

"We have to take a hard look at where it would be necessary or sensible to launch another major amphibious action again," Gates said. "In the 21st century, how much amphibious capability do we need?"

Loren Thompson, a defense analyst at the Lexington Institute, said the Marines need to replace their aging landing craft and there are no alternatives to the EFV.

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